In a non-generic device for separating an oil/water mixture disclosed in EP 0 148 444 A2, a pre-separation space is provided in which first the coarser components of the oil are separated from the mixture. The mixture precleaned in this way is then delivered to a coalescence chamber containing a plurality of coalescing bodies of an oleophilic plastic and being lighter than water. Extremely fine oil particles also settle on the oleophilic, specifically large surfaces of these bodies, flow together on the bodies and rise as larger, easily separable oil droplets into the separation space where they can collect and can be removed in the oil collection space. The water flows out of the separation space by a partition through another pipe. This device is large. Although oil separation is maintenance-free with the device over a longer time interval, the oleophilic coalescence bodies from time to time must be replaced by new ones. This replacement leads to downtimes of the system. With respect to the size of the system, the discharge performance on the oil and water which have been separated from one another is relatively low. Especially under cold ambient conditions and for moreover cold fluid mixtures to be separated the water removal performance, the rate with which water removal takes place is insufficient.
EP 0 733 389 B1 discloses a generic device for separating fluid mixtures, especially oil and water, with a vacuum tank in which this fluid mixture can be atomized by an atomization means. At least one liquid component of the fluid mixture after its separation can be drained from the vacuum tank. The corresponding other components can be suctioned in gas and/or vapor form out of the vacuum tank by the vacuum pump. The known atomization means has an atomizer nozzle for the fluid mixture. The liquid components can be drained by a hydraulic pump driven by a hydraulic motor, which form a structural unit located within the vacuum tank. The hydraulic motor can be driven by the fluid mixture which can be set into motion by another drive as soon as a definable fill level in the vacuum tank requires discharge of the component which is liquid at the time by the hydraulic pump. Based on the atomization means, it is possible to achieve almost optimum separation of the components with a small structural size of the device. Separation also is economically favorable with respect to energy input. Especially in applications at low and very low temperatures, the atomization means is fault-susceptible and is not especially well suited.